1. Field of the Invention
The present invention relates to an organic thin film transistor (OTFT) and a metal-insulator-metal (MIM) capacitor, and methods for manufacturing the same and, more particularly, to an OTFT and a MIM capacitor using silk protein as a dielectric material, and methods for manufacturing the same.
2. Description of Related Art
Thin film transistors (TFTs) are fundamental components in contemporary electronics, such as sensors, image scanners, and electronics display devices. In recent years, in order to decrease the production cost and increase the product application, organic thin film transistors (OTFTs) are rapidly developed which have the advantaged of low-cost and flexibility, can be produced in large-area.
The OTFTs can be divided into top contact OTFTs and bottom contact OTFTs. As shown in the FIG. 1, the top contact OTFT comprises: a substrate 10; a gate electrode 11 disposed on the substrate 10; a gate insulating layer 12 disposed on the substrate 11 and covering the gate electrode 11; an organic semiconductor layer 13 covering the entire surface of the organic semiconductor layer 12; and a source electrode 14 and a drain electrode 15 disposed on the organic semiconductor layer 13 respectively.
In addition, as shown in FIG. 2, the bottom contact OTFT comprise: a substrate 10; a gate electrode 11 disposed on the substrate 10; a gate insulating layer 12 disposed on the substrate 10 and covering the gate electrode 11; a source electrode 14 and a drain electrode 15 disposed on the gate insulating layer 12 respectively; and an organic semiconductor layer 13 covering the gate insulating layer 12, the source electrode 14, and the drain electrode 15.
In the conventional method for forming the gate insulating layer, the dielectric material is sputtered on the substrate and the gate electrode to from the gate insulating layer. However, the instrument for the sputtering process is very expensive and the process is complicated. In addition, the theoretical carrier mobility of the pentacene, which is the conventional material used in the organic semiconductor layer of the OTFT, is about 10 cm2/V-sec, and cannot match well with the carrier mobility of the conventional dielectric material. Hence, the actual carrier mobility of the pentacene in the pentacene OTFT is far below the theoretical mobility thereof. For example, when silicon nitride is used as a material of the gate insulating layer in the pentacene OTFT, the carrier mobility of the pentacene is lower than 0.5 cm2/V-sec. Even though aluminum nitride is used as the material of the gate insulating layer in the pentacene OTFT, the carrier mobility of the pentacene cannot be higher than 2 cm2/V-sec. Hence, it is impossible to manufacture OTFTs with high efficiency by using the present techniques and materials.
Therefore, it is desirable to develop an OTFT and a method for manufacturing the same, in order to prepare OTFTs in a simple and cheap way, and increase the efficiency of the OTFTs.
In addition, the metal-insulator-metal (MIM) capacitors are widely applied on digital and radio frequency (RF) circuit designs. Currently, several dielectric materials with high dielectric constant are developed to increase the capacitor density of the MIM capacitors and decrease the leakage current thereof.
As shown in FIG. 2, a conventional MIM capacitor comprises: a substrate 20; a first electrode 21 disposed on the substrate 20; an insulating layer 22, disposed on the substrate 20 and covering the first electrode 21; and a second electrode 22 disposed on the insulating layer 22. Herein, the conventional dielectric material used in the insulating layer of the MIM capacitor can be TiN, TiO2, SiO2, and SiN. However, when the aforementioned dielectric material is used as the insulating layer of the MIM capacitor, the insulating layer is formed on the metal layer by use of the sputtering process or the vacuum deposition equipment, which may cause the production cost and the process complexity increased.
Therefore, it is desirable to develop a MIM capacitor and a method for manufacturing the same, in order to prepare MIM capacitors in a simple and cheap way and apply on various digital and RF circuits.